An active type distance measuring device which determines a distance to a subject by projecting a light beam from the camera side and receiving reflected light from the subject, is generally known. When a PSD (semiconductor position sensor diode) is used as a light-receiving element of an active distance measuring device, it is necessary, in order to obtain the desired distance measuring accuracy, to ensure the required positional relationship between the optical axis of a light-receiving lens and the optical center of the PSD. However, a positioning difference may occur during mounting of the light-receiving lens and the PSD during the process of manufacturing the distance measuring device. In general, each individual light-receiving element is first soldered to a printed board, and then this printed board is attached to a holder of a distance measuring device. Therefore, a positioning difference is likely to occur when each light-receiving element is soldered to the printed board. In addition, since the light-receiving lens is manufactured to be slightly smaller in size than the lens holder in the stage of production so that the light-receiving lens is surely set in the lens holder, when the lens is attached, there may be a difference in the positional relationship between the optical axis 52 of the light-receiving lens 51 and the optical center 54 of the PSD 53, as shown in FIG. 5.
To solve the above-described problem, that is, to align the optical center of the PSD with the optical axis of the light-receiving lens during the manufacturing process, it has been conventional practice to move the PSD to a given position with a mechanical adjusting means or to make the light-receiving region of the PSD longer than is necessary so that the measured distance value cannot be influenced by the difference.
Employment of the mechanical adjusting means as described above, however, causes the device to be larger and more complicated.
An increase in the length of the light-receiving region of the PSD results in a reduction in the change of the ratio of the output signal to the measured distance. Accordingly, it becomes more likely that the output signal will be influenced by noise.